This morning I'm in Greensboro, NC. The temperature is just at freezing. It looked foggy. Then I wondered if the fog was mostly micro-ice crystals - perhaps suspended in the air or slowly falling downward. Then, I wondered how this was true could be proved. Most solutions I considered would affect the crystals - melting them if they were there - or form new ice crystals. This is kind of an uncertainty. Almost anything you can imagine to do may change what you want to prove. That is, you cannot see the micro ice crystals without changing them or creating them. So, how can this be done? BTW, how small can ice crystals be? Micro-size? Nano-size?
Random thoughts and used ideas